An automotive vehicle typically includes an engine control system that causes the engine to perform in accordance with various driver inputs. Known engine control systems may integrate several and/or all of mechanical, hydraulic, pneumatic, electric, or electronic sub-systems, to cause an engine to perform in a controlled fashion in accordance with driver inputs, consistent with performance characteristics inherent in the engine's own design. For example, an engine control system may control an engine's operation based on throttle position and engine speed. Throttle position, or an equivalent, represents a driver input, and in the case of an electronic engine control system, may be obtained from a throttle position sensor under control of the driver. Engine speed may be obtained from an engine speed sensor, or equivalent data source.
A control system may utilize those inputs to control engine operation in two different ways. For engine speeds less than a rated engine speed, the engine may be said to operate along a torque curve that corresponds to a corresponding amount of throttle, and for engine speeds greater than the rated engine speed, it may be said to operate along a speed regulation curve that corresponds to the corresponding amount of throttle. For example, for engine speed less than the rated engine speed and 100%, i.e. full or wide open, throttle, the engine may be said to operate along a torque curve corresponding to 100% throttle, and for engine speed greater than the rated engine speed, along a speed regulation curve corresponding to 100% throttle. For throttle settings less than 100%, the engine operates along torque curves and speed regulation curves that are correspondingly attenuated from those corresponding to 100% throttle.
An engine torque curve follows a characteristic pattern. In the low engine speed range, engine torque is low because of the engine's inability to charge and trap the larger air volumes that it does at higher speeds. Within an intermediate engine speed range, a torque curve peaks before the engine reaches rated speed, declining from its peak as engine speed increasingly approaches rated speed. Such a decline however may be considered beneficial to overall vehicle performance when viewed from the perspective of engine speed decreasing from rated engine speed toward peak torque speed because as engine speed decreases from rated speed toward peak torque speed, the torque increases. The amount of torque increase that occurs as engine speed falls from rated speed to maximum torque speed is sometimes called torque rise.
An engine speed regulation curve possesses its own particular pattern. With an engine operating under load at rated engine speed, a progressive reduction of the engine load to a zero load condition will cause engine speed to increase to a maximum zero-load speed that is approximately 10% to 15% above rated speed. Along an initial portion of a speed curve extending from rated engine speed, the rate at which engine speed increases as engine load decreases is relatively more gradual than along a final portion of that speed curve range that leads to maximum speed that is attained at zero load. In other words, as an engine that is initially running under load at rated engine speed is increasingly unloaded, its speed at first curtails relatively more gradually and then relatively less gradually, i.e. more abruptly, as maximum engine speed is approached.
It is believed that this characteristic form of engine speed regulation typifies that of engines in known vehicles and that it does not change as the drive ratio between the engine and the driven wheels changes, such as when a multi-gear transmission is shifted through a succession of different gears. Although it is known for a controller to change engine power settings when different transmission gears are selected, the inventor is unaware that such changes also change an engine's characteristic torque curves and engine speed regulation curves, as such curves have just been described above.
Continuing evolution of engine controls, particularly electronic microprocessor controls, allows the management of many more engine variables than simply those involving the quantity and timing of fuel injection. Such controls can, for example, also manage: the overall pressure of fuel injection; the pressure pattern during an injection event; a turbocharger for the engine; and the operation of emission control devices, such as an exhaust gas recirculation valve. While it may be known to program an engine controller with a complex of control choices for best meeting the often conflicting needs of engine performance, fuel economy, noise, and exhaust emissions, it is believed that the extent to which vehicle controls should be allowed to interact with an engine controller for improving one or more aspects of vehicle performance, including the feel of a vehicle to a driver, has not been fully appreciated by the state of the art.
A preliminary novelty search in connection with this invention developed the following U.S. Pat. Nos: 4,493,303; 4,593,581; 4,823,645; 5,257,193; 5,484,351; 5,496,227; 5,597,371; 5,603,672; 5,679,096; 5,720,358; and 5,738,606. Of these, U.S. Pat. Nos. 4,493,303; 5,257,193; 5,679,096; and 5,738,606 provide some background for appreciating the distinctive aspects of the present invention.
U.S. Pat. No. 5,257,193 relates generally to control of a transmission. Although engine performance curves are stored within a microprocessor, it does not appear that selection of a particular performance curve is made by the selection of a particular transmission gear but rather by another control that the driver uses to elect either a heavy load condition or a light load condition. Moreover, the disclosed use of this invention in a dump truck operating as a construction vehicle, and the nature of its drivetrain, said to comprise a lock-up torque converter and powershift transmission, suggest that the vehicle is other than a medium or heavy truck that operates along highways at highway speeds, perhaps instead being an off-road vehicle used in mining or major earthwork operations.
U.S. Pat. No. 4,493,303 relates to an electronic control then selects from a stored set of maximum power parameters in accordance with a sensed gear position of a transmission. While the present invention also utilizes transmission gear selection as an input to an engine controller, the detailed description of the present invention that presented in this disclosure will show that its principles are novel and uniquely distinctive.
U.S. Pat. No. 5,679,096 relates to a control for limiting engine torque in accordance with gear selection.
U.S. Pat. No. 5,738,606 relates to control of engine fueling in accordance with gear selection and/or in conjunction with driveline components of limited torque-carrying capacity. It appears that a selected performance limit is bounded within an engine performance map by a singular, fixed torque curve and speed regulation curve.